Sanding an arch in the top edge of the sidesMany guitars have flat soundboards. A growing number of builders use domed (spherical) tops. Mine are curved in the shape of a parabolic cylinder. That is, they are flat from neck to tail, but are curved side to side. Visit the design section to find out why.
I have a curved workboard that I use when bracing the top. I clip sandpaper to the same workboard and slide the sides back and forth over the sandpaper until the sides have a curve that matches the curve of the soundboard.